VoIP Ethernet Capture TMG3200

This article applies to:	Product	Version
	Tmedia	2.8, 2.9, 2.10, 3.0, 3.2

Capturing using the TMG3200's internal host

The TMG3200's internal host can be used for capturing packets that are mirrored from the VOIP0 and/or VOIP1 physical ports. This includes RTP traffic.

Preparing the Tmedia for capture

• If the traffic to be captured is on a VLAN, then an IP Interface with the services "MANAGEMENT" must be created.
  
  • The IP has to be static and on the same network as the one to capture.
    
  • The virtual port assigned must be the same as the port to capture. See IP Interface.

Start Capture

You need two SSH sessions to capture the traffic:

First, access the Tmedia management interface using SSH. Then, access the telecom baseboard using

telnet 172.31.1.1 

Prompt is now:

0/tbgw>

To capture VoIP0 traffic:

mv88eMonitor 0x4 0x4 8 600

To capture VoIP1 traffic:

mv88eMonitor 0x8 0x8 8 600

In the example the duration is 600 seconds, thus will capture traffic for 10 minutes.

Note: We don't recommend to keep the capturing for a long time. This is only for debugging purpose.

Second, access the Tmedia management interface using SSH
Prompt is now:

[root@TBxxxxxx ~]#

To dump the content of the VOIP traffic in the file voip_capture.cap
if the VOIP traffic is untagged:

tcpdump -i int0 -s 1500 -w voip_capture.cap

If the traffic is tagged, use the name of the IP interface created previously (for example vlan333)

tcpdump -i vlan333 -s 1500 -w voip_capture.cap

You will see something like this:

tcpdump: listening on mgmt0, link-type EN10MB (Ethernet), capture size 1500 bytes

Stop Capture

When you're ready, stop the capture by pressing control-C on the shell that was running tcpdump command
You will see something like this:

364 packets captured
590 packets received by filter
0 packets dropped by kernel

• Access the telecom baseboard from the Tmedia using telnet.

telnet 172.31.1.1

• Stop the capture

mv88eMonitor 0 0 0

Download Capture

To download the voip_capture.cap file, use SSH secure copy ("sftp") to the Tmedia management port. This can be done on Windows using tools like Filezilla or WinSCP.
The file will be located in

/root

References

• VoIP Ethernet Capture
• FreeSBC VoIP Ethernet Capture